1. Field of the Invention
The present invention relates to a technique for supporting a driver to drive a vehicle by providing an image capturing the surroundings of a vehicle to a driver.
2. Description of the Related Art
In a know technique for supporting a driver to drive a vehicle by providing an image capturing the surroundings of the vehicle, at least one camera for capturing the surroundings of the vehicle is mounted on the vehicle and an image captured by the corresponding camera is provided to an operator (i.e., the driver) (e.g., Japanese Unexamined Patent Application Publication 2002-328021).
In another known technique, by applying an observing-point conversion to images of the surroundings of a vehicle captured by a plurality of cameras, by synthesizing them into an image to be obtained when captured at an observing point above the vehicle, and by placing a figure representing the vehicle on the synthesized image, an overhead image representing the surroundings of the vehicle in an overhead viewing manner is generated and provided to an operator (e.g., Japanese Unexamined Patent Application Publication 2002-354468).
More particularly, in this technique, for example, when the vehicle moves backwards in a parking lot as shown in FIG. 5A, by capturing obliquely downward surroundings of the vehicle with wide angle cameras 501 and 502 installed at the front and rear and 503 and 504 at the right and left of the vehicle, by applying an observing-point conversion and a synthesis to the respectively captured images, an image viewing the parking lot from overhead is generated. Then, an image, as shown in FIG. 5B, is generated by placing a figure 511 representing the vehicle on an image 510 viewing the parking lot from overhead and is provided to the operator as an overhead image.
Instead of the plurality of cameras for generating such an overhead image, in another known technique, a camera capturing the entire circumference of the vehicle is provided.
According to the techniques for providing an operator with the overhead image, the overhead image allows the operator to intuitively grasp surrounding circumstances of the vehicle and the relationship between the vehicle and a body in the surroundings.
However, it is hard to grasp the distance between an actual vehicle and an obstacle in the surroundings from an overhead image. Hence, only with the overhead image, an operator has difficulty in determining, for example, whether the vehicle manages to go along the side of the obstacle with a hairbreadth. In addition, it is difficult to generate an overhead image so that the relationship between the figure representing the vehicle on the overhead image and the obstacle included in the image exactly agrees with that between an actual vehicle and an actual obstacle in the surroundings of the vehicle.
In particular, when a tall obstacle 520 exists in the vicinity of the vehicle as shown in FIGS. 5C and 5D, on an overhead image undergoing an observing-point conversion, the obstacle is displayed as a figure 521 occupying all of a certain angle range with respect to a camera capturing the obstacle, in a different manner from that of the case where, as shown in FIG. 5E, the surroundings of the vehicle are actually observed from above the vehicle. Hence, the operator is unable to intuitively and accurately grasp the position and the shape of such an obstacle from the overhead image.